Well im sick of trying everything, and im about to give up of bt4

I had win7 and ubuntu on my laptop so i did this:
- run bt4
- run install
- in partitions deleted the ext3 and swap from ubuntu, created the 2 new for bt4
- install successfull and rebooted
-on grub loader, appeared the ubuntu lines... and not the bt4 ones

Tried many ways to solve this shit, and my desperate one

# dd if=/dev/zero of=/dev/sdX bs=512 count=1
So lost all, instaled win7 again
installed fresh new bt4
and guess what, in grub still appear Ubuntu in the list... wth?

So how can i really remove grub so bt4 install make a fresh new one, or how to fix the current grub?

Thanks in advance.